Roughly 5,200 U.S. troops will be deploying to the southern border in response to the migrant caravan pushing north through Mexico, U.S. officials told Fox News on Monday.

Air Force Gen. Terrence O’Shaughnessy, head of U.S. Northern Command said at a press conference in Washington, D.C. that “We’ll reinforce along priority points of entry so as to enhance [Border Patrol]’s ability to harden and secure the border.” Adding that the deployment would be completed by the “end of this week.”

The reinforcements headed to the U.S.-Mexico border are reported to be support troops – not combat troops – and will include three engineering battalions with “heavy equipment”, and aviation and medical personnel.

Most of the troops headed to the wall are on active duty and will carry weapons, but will not be part of any law enforcement effort in deference to the Posse Comitatus Act, which strictly prohibits the federal government from using the armed forces in a domestic police role.

The number represents a significant increase over the initial estimate of 800 that was reported last week.

There are three planned staging areas: in South Texas, Arizona and California, for what’s now been dubbed Operation Faithful Patriot. The mission’s U.S. ground commander is Army Lt. Gen. Jeffrey S. Buchanan, who was sent to Puerto Rico last year to lead Hurricane Maria relief efforts.

The troops are coming from military posts including Fort Bragg, Joint Base Lewis-McChord, Fort Stewart, Fort Campbell, Fort Riley and Fort Knox. They include three medium-lift helicopter companies with night vision equipment. O’Shaughnessy added that 22 miles of barbed wire had already been sent to the southern border and Air Force C-130s and other cargo planes would be used to deliver additional Border Patrol personnel.

Defense Secretary James Mattis on Friday approved a request for assistance from the Department of Homeland Security.

Mattis’ statement said the military will help U.S. Customs and Border Protection (CBP) with planning, engineering such as fencing and other barriers, aircraft to move CBP personnel, medical treatment for migrants, command and control, housing for CBP and protective equipment for Border Patrol officers.

Speaking to reporters traveling with him Sunday, Defense Secretary James Mattis said the Pentagon is currently in the planning stages of the mission.

“What’s the material requirement, how many troops are needed, break it down like that,” Mattis said. “The meetings are going on. The orders are being drafted and some material is moving, construction-type material, 30 barriers, that sort of thing that they may need. We anticipate from what they thought they’ll need. I’ll come back to you when we have it finalized, the details, the rules that the troops will be under, I’ll give that. I do not have that at this time.”